In the processing of semiconductor devices, such as transistors, diodes, and integrated circuits, a plurality of such devices are fabricated simultaneously on a thin slice of semiconductor material, termed a substrate or wafer. Such wafers are extremely brittle and easily contaminated. During manufacturing of semiconductor integrated circuits, therefore, care must be taken to avoid physical damage and particulate contamination to the wafers.
Various systems are known for handling wafers within semiconductor processing systems. The particular application or environment from which the wafer is lifted often determines the type of pickup device. One class of pickup devices, known as Bernoulli wands, are typically used for high temperature applications. Bernoulli wands utilize jets of gas downward from the wand toward the wafer to create a region of low pressure above the wafer, therefore lifting it. The advantage being that the hot wafer need not contact the pickup wand, except perhaps at one or more small locators depending underneath the wand. Such a Bernoulli wand is shown in U.S. Pat. No. 5,080,549 to Goodwin, et al.
Another type of wafer pickup wand utilizes a vacuum force and thus must be in intimate contact with the wafer. U.S. Pat. No. 4,566,726 to Corenti, et al., discloses a combination Bernoulli and vacuum-type pickup device.
A third type of wafer pickup device is a simple paddle augmented with a vacuum which supports wafers from underneath. Such a paddle is illustrated in U.S. Pat. No. 4,951,601, to Maydan, et al. This patent also illustrates a typical movement device for translating wafers from location to location within processing systems. The wafer handler is capable of linear retraction and extension, as well as rotation about an axis.
U.S. Pat. No. 5,135,349 to Lorenz, et al., discloses a robotic handling system utilizing two paddle style pickups mounted on a common rotating base. Both pickups are adapted to extend linearly away from one another to speed up handling of wafers within the processing system. Again, the paddles are augmented with a vacuum generated through a plurality of holes in an end effector portion of each paddle; the vacuum being transmitted along a channel within the paddle.
There are two main drawbacks to prior wafer handling systems. A single wafer handler may not be appropriate for picking and placing wafers into or out of particular processing environments. That is, a Bernoulli wand might be suitable for high temperature environments, but has a relatively high profile which may limit its maneuverability between closely spaced wafers. Furthermore, rotating handling robots, such as the ones shown in the patent to Maydan, et al., require a significant amount of horizontal room to maneuver. Although the device in the Maydan patent is a multiple chamber processing system, many systems only include a single processing chamber, and thus such a rotational wafer handler is inefficient.